Strategic Exploitation of Heme Acquisition by Gram-positive Bacteria from Human Host

Iron is an essential nutrient for microorganisms that plays a vital role in pathogenesis during the course of an infection. One of the primary defense strategies of mammalian hosts against bacterial infection is to limit the availability of free extracellular iron. The largest reservoir of iron in human is heme, which is complexed with hemoglobin. Numerous high-affinity heme-scavenging pathways are employed by pathogenic bacteria to acquire iron. Mutations in these pathways often result in attenuated virulence. A limited understanding of heme uptake mechanisms is available for Gram-positive bacteria as the study of heme acquisition was restricted to Gram-negative bacteria for many years. This review summarizes some of the old and new investigations covering the uptake, transport and degradation of heme in several Gram-positive bacteria.